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ABB develops new cost of ownership formula for electric motors

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Hydrocarbon Engineering,

ABB has devised a new formula, which shows that the cost of ownership is the purchase price plus the cost of running and the cost of not running, to help motor users to make more informed purchasing decisions. The company has launched a campaign to raise awareness among end-users about the true cost of owning electric motors, and to educate OEMs and end-users about the different elements that should be considered outside of just purchase price.

Total cost of ownership is made up of a combination of the purchase price, the cost of running the motor in terms of the energy consumption over its lifetime and the cost to a business if that motor fails to run when needed. For example, a 45 kW motor costing £1700, with 94.1% efficiency and running for 6000 hours per annum would cost £2 105 454 over a 20-year life. This assumes an average electricity price of £0.08 and the downtime cost per annum of around £80 000.

When expressed as purchase price over total cost of ownership the resulting ratio is very small. For example, if the ratio was one, then this would mean that the purchase price was the same as the cost of ownership. But in the above example, you end up with a ratio of 0.0008. Given such a high ratio, the true cost of owning a motor in a critical continuous process application is far more important than the initial purchase price. Buyers should therefore focus on the efficiency and the reliability of the motor.

The biggest risk, and the highest cost, for the motor owner is the cost of not running and unplanned outages through motor failure. High efficiency alone is not necessarily a guarantee of high reliability. Consideration must be given when choosing a motor to the full load operating temperatures of the windings and the bearings.

End users and OEMs need to also think about how motor manufacturers can assist to predict when critical motors will fail thus, through onsite or remote condition monitoring and analysis, service interventions can be planned during scheduled plant outages. And if the worst comes to pass and the motor fails between planned outages consideration should be given to how the manufacturer can get you running again as quickly as possible.

Using the total cost of ownership calculation is not suitable for all motor users, only those that have critical motors running long hours. Nonetheless end-users and OEMs alike should have the information to hand to be able to make informed choices.

Adapted from press release by Rosalie Starling

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